How to use enum flags in C#

For example:

FilePermissions permissions = FilePermissions.Read | FilePermissions.Write;

In this article, I’ll show how to create and use enum flags.

Use [Flags] attribute on enum type

To enable an enum to hold multiple values:

• Add the [Flags] attribute to the enum type.

• Assign integer values as powers of 2.

• Optionally include None = 0 to represent no values set.

For example:

[Flags]
public enum FilePermissions
{
    None = 0,
    Read = 1,
    Write = 2,
    Execute = 4,
    Delete = 8
}

This example represents different file permissions. The reason values are powers of 2 is that they correspond to bit positions in binary representation:

[Flags]
public enum FilePermissions
{
    None = 0b0000,  // 0
    Read = 0b0001,  // 1
    Write = 0b0010, // 2
    Execute = 0b0100, // 4
    Delete = 0b1000  // 8
}

Since each value corresponds to a bit position, bitwise ORing them together allows multiple values to be stored in a single variable. For example, FilePermissions.Read | FilePermissions.Write results in the following binary operation:

0001  (Read)
|
0010  (Write)
-----
0011  (Read & Write)

Use HasFlag() to check if a value is set

To check if an enum contains a specific value, use HasFlag():

FilePermissions permissions = FilePermissions.Read | FilePermissions.Write;

if (permissions.HasFlag(FilePermissions.Read))
{
    Console.WriteLine("Has Read permission!");
}

if (permissions.HasFlag(FilePermissions.Write))
{
    Console.WriteLine("Has Write permission!");
}

Output:

Has Read permission!
Has Write permission!

Alternatively, you can check using bitwise AND:

if ((permissions & FilePermissions.Read) == FilePermissions.Read)
{
    Console.WriteLine("Has Read permission!");
}

You can add more values to the enum at any time using bitwise OR:

FilePermissions permissions = FilePermissions.Read | FilePermissions.Write;

if (!permissions.HasFlag(FilePermissions.Execute))
{
    permissions |= FilePermissions.Execute;
}

Console.WriteLine(permissions.ToString());

Output:

Read, Write, Execute

Using enum flags simplifies working with multiple values, making code more readable and efficient.